The anti-inflammatory and anti-proliferative activity of the naturally occurring triterpenoid, oleanolic acid, has been improved by chemical modifications. For example, 2-cyano-3,12-diooxooleana-1,9(11)-dien-28-oic acid (CDDO) and related compounds have been developed (Honda et al., 1997; Honda et al., 1998; Honda et al., 1999; Honda et al., 2000a; Honda et al., 2000b; Honda, et al., 2002; Suh et al. 1998; Suh et al., 1999; Place et al., 2003; Liby et al., 2005) and evaluated in clinical trials for the treatment of cancer, diabetic nephropathy and chronic kidney disease.
Synthetic triterpenoid analogs of oleanolic acid have also been shown to be inhibitors of cellular inflammatory processes, such as the induction by IFN-γ of inducible nitric oxide synthase (iNOS) and of COX-2 in mouse macrophages. See Honda et al. (2000a); Honda et al. (2000b), and Honda et al. (2002), which are all incorporated herein by reference. Synthetic derivatives of another triterpenoid, betulinic acid, have also been shown to inhibit cellular inflammatory processes, although these compounds have been less extensively characterized (Honda et al., 2006). The pharmacology of these synthetic triterpenoid molecules is complex. Compounds derived from oleanolic acid have been shown to affect the function of multiple protein targets and thereby modulate the activity of several important cellular signaling pathways related to oxidative stress, cell cycle control, and inflammation (e.g., Dinkova-Kostova et al., 2005; Ahmad et al., 2006; Ahmad et al., 2008; Liby et al., 2007a). Derivatives of betulinic acid, though they have shown comparable anti-inflammatory properties, also appear to have significant differences in their pharmacology compared to OA-derived compounds (Liby et al., 2007b).
In general, it is not certain that the triterpenoid starting materials employed to date have optimal properties for all applications compared to other possible starting materials. In addition, it is often necessary to synthesize triterpenoid derivatives from natural product starting materials. The production of highly purified triterpenoid starting materials can be expensive, and the plant materials that are the ultimate sources of these compounds can vary in availability, including due to adverse weather conditions, disease, and other environmental factors. Given that the biological activity profiles of known triterpenoid derivatives vary, and in view of the wide variety of diseases that may be treated or prevented with compounds having potent antioxidant and anti-inflammatory effects, and the high degree of unmet medical need represented within this variety of diseases, it is desirable to synthesize new compounds with diverse structures that may have improved biological activity profiles for the treatment of one or more indications. Therefore, the design of potent, selective antioxidant/anti-inflammatory compounds that can be readily synthesized from simple starting materials is a desirable goal.